Rebuilding CR125 bottom end

I will be rebuilding the bottom end of my 2002 CR125 on Friday (going to ride on Saturday), something I have never done before. I have already split the cases and pulled the crank so that's not a problem. But since I don't have a service manual for it, I was wondering if I could somewhat rely on my 2005 CR250 manual for the reinstall? Also would this article mostly apply too?


I'm not so much worried about the top end, just the cases.



Two strokes are all relatively easy to work on and are cheaper for parts, which is why they are amazing and better than 4 strokes :thumbsup:. You always know a little about whats behind the next cover buuuuutttttt i know my manual has got me out of some sticky situations on the order of things and that transmission might be hard to remember unless you keep it together while its out. Just saying, you better have a good memory if you plan to do it without a manual.   

Edited by ljohnllc

take pix while taking apart so you can refer back when putting together.

Thanks guys, everything went smoothly. Aside from the main bearings. Even left overnight in the freezer and heating the case with a propane torch they wouldn't drop in. So I had to use a press and a big socket.The crank puller was also a must.


But now we discovered that the oil drain bolt is stripped. Is it possible to helicoil the case? Has anyone ever done it?

Yes, just follow the instructions on the package.  Youtube it if you have never done it before.

Yes, just follow the instructions on the package.  Youtube it if you have never done it before.

I did it for the 1st time the other day for an oil filter bolt on a CRF250. But I had the cover in my hands and used a drill press. This one will have to be done by hand.


Plus the tang at the bottom had to be punched out. How can that be done without losing the tang in the transmission?

Drill slow with tons of grease on the bit to catch the metal flakes.


As far as the tang, you can use needle nose pliers to snap it and pull it out.  Practice on one before you try.

Will do! Thanks!

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